In organizations receiving large amounts of mail, the opening of envelopes constitutes a substantial burden. To deal with this burden, mechnical envelope openers have been used which operated by cutting a thin strip from one edge of each envelope. Such openers sometimes damage the envelope contents because of variations in envelope size and the manner in which the contents are stuffed in the envelopes. Mechanical openers also produce large volumes of paper shavings from the high speed cutting of envelopes.
It has also been proposed to open envelopes by processes involving the chemical degradation of paper, and specifically of its cellulose, at at least one edge of the envelopes, and preferably at three edges thereof, followed by mild mechanical action to remove the degraded paper.
Zacker U.S. Pat. No. 2,866,589 discloses the degradation or cellulosic paper envelopes at their edges by chemical reagents, specifically by the action of nitric acid, sodium hydroxide, or sodium hypochlorite, or by the action of sulfuric acid followed by the application of heat. These materials are caustic on contact to human skin and/or produce noxious fumes. Their use within a confined space and the handling of the envelopes after chemical degradation are therefore hazardous, particularly with unskilled personnel.
Whitman U.S. Pat. No. 3,871,573 teaches the utilization of successive applications to the edges of an envelope of a sodium alkyl sulfate and an organic acid, such as oxalic acid or acetic acid, followed by the application of heat. Gunther, Jr. U.S. Pat. No. 4,069,011 discloses a similar system, utilizing tartaric acid in combination with the sodium alkyl sulfate. These systems produce sulfuric acid in situ and are also hazardous to use because of the sulfuric acid fumes produced and because residual sulfuric acid on the envelopes can be harmful to the hands in the subsequent handling of the envelopes. In addition, the sodium alkyl sulfate is a relatively expensive material and the two-stage application is more complex than a single chemical application. Finally, the production of sulfuric acid in the process is corrosive to the equipment used.